The present project will study the mother-child interactions of normal and hyperactive children using an objective coding system for recording social interactions. The effects of age and type of setting (free play and task) on these interactions will also be examined. This will permit the development of a standardized clinical evaluation device for the assessment of the interactions of hyperactive children with their parents. The hyperactive children will then participate in a triple-blind, drug-placebo crossover design to determine the effects of two doses of Ritalin, a stimulant drug, on the mother-child interactions of these children. Subsequently, another group of hyperactive children will participate in a triple-blind, drug-placebo crossover study to evaluate and compare the effects Ritalin and Dexedrine on the mother-child interactions of these children. In both drug studies, the data will also be analyzed to determine predictors of drug improvement in the children.